If your heart is not set on the Micro you could use the Nano or the Mini. Both have a smaller footprint than the Micro
The Mini is quite small but requires an FTDI to program (not a big deal). I2C pins (A4&A5) stick out on top of the chip and can be attached with two female wires. It comes in both a 3.3v and 5v model. The 5v however lacks a 3.3v output (a gotcha I found out too late).
Here is a size comparison with the Micro on a breadboard